Method and means for honing gears, and for truing the honing means



Jan. 18, 1938.

METHOD AND MEANS FOR HONING GEARS, AND FOR TRUING THE HQNING MEANS Filed Jan. 4, 1935 4 2%672372 jw/Wd QMh E. STUB'BS 2,105,896

Patented Jan. 1 8, 1938 PATE N'l. OFFICE METHODv AND MEANS FOR HONING GEARS, AND FOR TRUING' THE HONING MEANS Everard Stubbs, Springfield, Vt., assignor to The Fellows Gear Shaper Company, Springfield, a corporation of Vermont Application January 4, 1935, SerialNo. s97

' 3 Claims. (01. 51-204) This invention relates to the finishing of gears, ear shaper cutters, and other machine elements analogous thereto in being capable of running in mesh with gears or of being cut by gear shaper utters. It is particularly concerned with the orrection of errors of tooth face form, tooth spacing, and tooth thickness and the removal of surface imperfections such as tool marks in articles of the character specified, to bring them to the highest possible quality of accuracy and perfection of finish.' It comprises a new method; that of honing as distinguished from the previously used methods of finishing gears and the like by grinding, lapping or burnishing. It

' comprises further a new type of tool; namely, a

tool in the form of a gear conjugate to the gear or other machine element or gear cutter to be finished, and composed not of metal but essentially of abrasive mineral matter of sufficiently granular structure to remove minute chips from the hardest of metal gears, gear cutters, etc., in-

luding those of alloy steels which have been hardened by heat treatment. The invention further comprises the method of truing such tools to correct errors resulting from wearing away of their tooth surfaces when in use.

fully disclosed in the following specification, with eference to the drawing, and defined in the appended claims.

In the drawing,- Fig. 1 is a diagrammatic perspective view illustrating the general principles of a machine suitable for performing the gear finishing method with the aid of honing tools embodying the tool phase of the invention;

Fig. 2 is an end view of a gear in association with three honing tools bywhich the gear is to be finished;

Fig. 3 is a perspective view of a gear and a honing tool having internal teeth, in operative relationship to one another;

Figs. 4 and 5 are fragmentary sectional views of a tool conforming with the invention; the

ection of Fig. 4 being perpendicular to the axis of the tool and that of Fig. 5 being radial.

The operation of finishing a gear in accordance with the principles of this invention may be performed by a wide variety of mechanical means.

n other words,'the invention does. not consist in a new organized gear finishing machine, but in a new type of tool and a new method performed with the aid of such tool or a plurality of tools. Hence I show herein, and diagrammatically, only 0 much of a typical machine as sufiices to illusone of the tools directly, and drive the work trate an arrangement of tools and work, and the movements thereof, by which the finishing method may be performed.

Referring now to Fig. 1, a gear to be finished is shown at a in mesh with two of three honing 5 tools, I, 2 and 3, which may be spaced equiangularly around the axis of the'work in the manner shown in Fig. 2. The third tool is omitted from Fig'. 1, for clearness of illustration. The work piece a is mounted on a spindle 4 which is rotated by suitable means, as an electric motor 5 acting through pulleys 6 and 1, a belt 8, shaft 9, and helical gear couple Ill, H. The tools i and 2 are mounted on spindles l2 and I3 respectively which rotate in bearings suitably located to hold the tools in proper mesh with the work, and may be provided with brakes or equivalent retarding means to resist rotation of the tools in such degree as will exert a desired pressure between the contacting tooth faces of the work piece and tools. While in this instance the workpiece drives the tools against such resistance as is afforded by the retarding means, it will be understood that power may be applied to rotate piece and the other tool or tools through their intermeshing teeth. The third tool of the group herein contemplated (to be located as shown in Fig.- 2) is mounted on a similar shaft, similarly. supported in a location spaced equally from the shafts I2 and |3 in angular rotation about the work spindle axis. 7

The work spindle may be simultaneously reciprocated axially to pass the work piece back and forth lengthwise of the teeth of the tool, by a gear segment I4 meshing with rack teeth IS on the spindle'and driven from the gear element III by an intermeshing gear l6, shaft l'l, gears l8 and I9, shaft 20', crank 2|, connecting rod 22, and crank arm 23 on the shaft 24 to which said'gear segment also is secured.

The central new feature of the invention consists in a tool having gear teeth conjugate to the tooth elements of the pieceto be finished and constructed essentially of non-metallic abrasive material. Such material may be grains of hard mineral matter, natural or artificial, such as emery, corundum,si1icide of carbon, or analogous suitable substance, agglomerated and held together by a strong and rigid bond. Any material which, when in the form of agglomerated or straight from' end to "form of external gears.

- work piece a.

of natural stone which has a sufficiently dense and homogeneous structure and a proper grade and hardness for the purpose.

Tools containing the invention are produced from blank disks, cylinders or rings of the ag-' glomerated mineral or of natural stone, by cutting teeth therein; in the outer circumference for making an externally toothed tool, or the inner circumference of an annular blank when making an internal tool. I have devised a special tool for initially cutting or roughing out such teeth which forms the subject of a separate application for patent filed by me. After being initially cut, the teeth of externally toothed tools are preferably finished by generative rolling motion in contact'with the face of a grinding wheel made of abrasive of suitable grit and grade to break or cut away excess material from the tooth faces of the honing tool in course of production. When the teeth being made are of involute form, the face of such grinding wheel is a plane. Internally toothed honing .tools cannot be finished in that manner, but they are satisfactorily finished (and so may externally toothed gears be alternatively finished) by being run in mesh with a conjugate honing tool while. relative axial reciprocation is effected between the two intermeshing tools.

In this specification the term grit and grade is used with the meaning understood in the art of grinding wheel manufacture. It includes the factors of hardness of the mineral, size of the agglomerated grains, and the rigidity and tenacity of the bonding medium by which such grains are held together. Differences with respect to one or more of these factors enable one abrasive tool to cut away the material of another, whether by dislodging bodily grains from u the surfaces of themember being operated on, or by cutting away-the protruding parts of such grains without dislodging the entire grains. Speed of travel is also a factor causing thesurfaces of the toothed honingtool to be cut away and smoothed in the case where such a tool is finished by the action of a grinding wheel rotating at high speed. The qualities thus included within the meaning of the term grid and grade fund of knowledge in these matters possessed by those skilled in the art of grinding tool manufacture for the production of toothed honing wheels of the character herein described which will be capable of finishing to truth and accuracy the teeth of other honing tools of the same nature but of diiferent grit and grade.

The teeth thus formed in honing tools according to this invention may be either helical end; and if helical may lead as needed to finish helical gears, hour glass worms, etc. of different characters. Of course the tools may be'made of any ,diameter and thickness and provided with teeth of any pitch and pressure angle, conjugate to all descriptions of helical and spur gears.

The tools shown in Figs. '1 and 2 are in the It is part of my contemplation, however, to make them as internal gears, and such a tool is shown at 25 in'Fig. 3 clamped in a holder 26 which may be rotatably mounted in any suitable hearing or support, in which case thetool is driven rotatably by the Conversely, internal gears may be finished by cooperation with a honing tool in the form of an external have any helix angle or are selected in accordance with the gear, in an arrangework piece for the tool.

It is also a part of the invention to make different parts of any single honing tool, whether externally or internally toothed and of straight or helical formation, with-different qualities of grit and grade in different portions. For instance, such different parts may be located in zones perpendicular to the axis of the tool, as indicated at la, lb and la in Fig. 5. The zones in and la may be of such quality as to have a more pronounced cutting action on steel than the zone lb, in order to impart a crowning formation to the side faces of the teeth of a metal gear. or the materials differing from one another in grit and grade may be located in zones concentric with the axis of the tool as shown at id, Ie and If in Fig. 4. The zone If may include the pitch circle on .Which the honing tool meshes with the work piece, and may be of a quality to cut more effectively than the adjacent zones in order to compensate for the absence of radial slip between mating teeth of tool and work piece at the pitch circle. These specific illustrations typify the general principle that a single tool embodying the invention may be made with different parts of different grit and grade of any desired qualities, located in any desired positions with relation to one another, suitable for the result desired.

The number and arrangement of tools described with reference to Figs. 1 and 2 are not limiting factors of the invention; for the gearsimultaneous mesh with the work piece. Also different ones of a plurality of tools in such simultaneous mesh may be so formed as to meet with the work piece on different pitch circles, in order to obtain radial cutting eifect in all parts of the tooth surface.

For finishing standard gear shaper cutters having side clearance, different tools may be used upon the opposite sides of the cutter teeth; such tools being respectively complemental to the different helix angles of the opposite sides of a helical cutter, or complemental to the helicoids of opposite hands forming the opposite tooth faces of a cutter designed for generating straight spur gears.

Other gear elements of wide variety, other than those before-described, may-be finished according to the same process and by honing tools of essentially the same character.

I have found in practice thatv tools of this character, operated as described, give remarkable effect in the finishing of metal gears, hour glass worms, gear shaper cutters, and the like, of all qualities, including those made of hardened steel alloys. They rapidly remove excess stock and surface irregularities from the work pieces and bring the latter into a condition of extreme truth and accuracy in a surprisingly short space of time. The action is unlike that of the convenand such high speeds have been found byexperience to be the necessary and correct cutting speeds. In the present case, however, I have discovered and demonstrated the new principle herein described; viz., the gears and the like may be finished by intermeshing rotation with a conjugate gear of abrasive material, and simultaneous relative axial reciprocation, when the relative movement between the contacting surfaces is comparatively slow, for instance in the order of from 200 to 500 strokes per minute.

In this finishing process, the contact faces of tool and work are lubricated and flushed by a freely flowing liquid, preferably of an oily nature. I have used kerosene oil for this purpose and have found it eminently satisfactory.

In the process as hereinbefore described, the native cutting qualities of the abrasive tools, that is the sharp edges or points of theirconstituent grains, are alone relied on for cutting the work. I have found, however, that such tools operate excellently with a free abrasive carried in a liquid medium. The tooth surfaces of the abrasive tools contain cavities between the constituent grains. These cavities are irregularly distributed over the entire extent of the tooth surfaces and are located close to one another. The particles of free abrasive enter these cavities and lodge on the bounding edges thereof, by which they are firmly supported. That is, the free abrasive does not roll between the surfacesof the tool and of the work, as in the case of lapping tools of the prior art, but is mainly held by the ledges or shelves provided by the boundaries of these cavities, so that the particles are carried bythe tool and form minute cutting edges and points on the operative faces of the tool. The tool constitutes a fine and accurate holder for the particles of loose abrasive, and is so hard and rigid that it is not itself readily broken down and deformed by such particles.

There is, however, some slight breaking dow rial of suitably different grit and grade to havea cutting effect on the tools to be trued. Such a 'truing tool may be substituted for the work piece a, in a machine of the character shownin Fig. 1, to correct externally toothed honing tools of the type shown in Figs. 1 and 2. Or one may be substituted for the Wuik piece 'shown in Fig. 3 to correct an internally toothed honing tool.

What I claim and-desire to secure by Letters Patent is:

1. A gear finishing tool consisting of an abrasive member having gear teeth conjugate to those of the gear to be finished, an compdsed of nonmetal mineral grains suitable to abrade steel, bonded together, such grains in different zones of the tool teeth being difierent from one another in steel cutting capabilities.

2. A gear finishing tool consisting of an abrasive member having gear teeth conjugate to those of the gear to be finished, and composed of nonmetal mineral grains suitable to abrade steel, bonded together, different parts of such teeth, in zones concentric with the tool, being composed of different grades of abrasive material'having respectively different steel cutting qualities.

3. A gear finishing tool consisting of an abrasive member having gear teeth conjugate to those of the gear to be finished, and composed of nonmetal mineral grains suitable to abrade steel,

bonded together, different parts of the tool'tc-eth in zones between planes whiotf'are perpendicular to the axis of the tool being composed of abrasive grains having respectivelydifierent steel cutting qualities.

EVERARD STUBBS. 

